I'm putting new moser axle shafts in my full width F150 9". I bought the axles with the set 20 bearings and seal installed. When put into the axle housing, and using the original drum brake backing plate as a spacer, there is still about 1/8" to the change in diameter where the rectangular retainer plate seats. So, if I tighten down the bolts, it will bow the plate and pull the bearing cone into the cup with no running clearance.

I just got off the phone with Moser and the guy there tells me this is normal and not to worry.